Antisemitic messages and offensive remarks are being posted on social networking site Twitter in France as part of a "concerning" new trend.

The president of the Union of French Jewish Students urged Twitter to improve its moderation system after French users of the site began competing with each other to post messages under the hashtag #unbonjuif.

The term is translated as a "a good Jew," but in the last few days it has been employed next to comments such as "a good Jew is a dead Jew" or alongside photographs of concentration camp victims. Another read: "A good Jew can pump up your tyre with his nose".

Jonathan Hayoun, UEJF president, said it was time for Twitter to take responsibility and join the fight against "the scourge" of antisemitism, and called for a meeting with the company.

"Twitter France must ensure that messages that convey racist or antisemitic hate speech are not highlighted or available to all of its social network," he said. "The fight against racism and antisemitism is everyone's business, starting with those that regulate social networks."

Paris-based anti-prejudice group SOS Racisme said it was deeply shocked "by the wave of feverish hatred spread on Twitter these days".

A spokesman added that freedom of expression could not be invoked when it came to "endangering life or personal integrity".

The hash tag became the third most popular one in use yesterday on Twitter in France.

"Twitter is fast becoming the Internet’s distribution platform of choice for bigots who use it to get their messages of hate out in 140 characters or less," said Abraham Foxman, national director of the Anti-Defamation League. "Twitter’s terms of service lag far behind other established social media platforms in setting standards which would provide a basis for Twitter to block or remove racist, hate-filled tweets and re-tweets."

Its use comes in the wake of a brutal attack on a Jewish man in Paris over the Rosh Hashanah period. The man was beaten by two attackers and left unconscious.

A spokesman for Twitter said: "Twitter does not mediate content. If we are contacted directly by local law enforcement about potentially illegal content in a specific market, we will evaluate the reports on a case by case basis."